Accelerator Physics
Accessing the symmetric component of quadrupole misalignment through counter-rotating closed orbits in EDM storage rings
Ibrahim Abedrabbo and Selcuk Hac{\i}ömeroğlu
In the storage ring proposed to measure the
proton electric dipole moment (EDM), quadrupole misalignments of a few microns mimic a genuine EDM through a
geometric (Berry) phase; at a 10 micron rms misalignment the false signal is up to a thousand times the target sensitivity of 1e-29 e-cm. The misalignment splits into an antisymmetric component, which distorts the closed orbit and is visible to the beam-position monitors, and a symmetric component, whose orbit signature is strongly suppressed. Standard single-beam orbit correction therefore removes only the antisymmetric part. The proposed design reaches the symmetric one by beam-based
alignment (BBA), which is effective but relatively slow and invasive. Using
symplectic beam and
spin tracking, we show that correcting the two counter-rotating beams jointly recovers the symmetric component from the orbit itself; it is carried by the sum of the two orbits, whereas their difference is blind and a single beam is far too weak to recover it. The static BPM offset is degenerate with the symmetric misalignment in this sum, so the scheme does not replace the initial absolute
alignment. However, the drift is differential and the offset cancels, so continuous two-beam correction maintains the
alignment after a single initial BBA calibration, reducing the repeated realignment required by the original
proton EDM proposal.
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Applied Physics · Cross-listed from cond-mat.mes-hall
Methods for traceable scanning magnetometry using single nitrogen vacancy centers in diamond: determining orientation, distance and localization
Nikhita Khera, Ephraim Spindler, Yanis Abdedou et al. (+7 more)
Individual, scannable nitrogen vacancy (NV) centers in single
crystal diamond nanostructures enable nanoscale, quantitative imaging of
magnetic stray fields. Nevertheless, important parameters like distance between the NV center and the sample and the orientation of the NV high
symmetry axis are often not known precisely and enter data evaluation as free fitting parameters. We here use scanning NV imaging on micro-patterned, perpendicularly magnetized stripes and discs. From these measurements, we directly infer NV - sample distance d_NV and the NV's azimuthal orientation without the need for an external vector magnet control. We determine d_NV = 31.5 nm, while we infer the azimuthal orientation with a precision of 3{\deg}. We additionally employ commercially available silicon needles to image the apex topography of our diamond nanostructures to detect surface contamination. Simultaneously, monitoring NV fluorescence as a function of the needle's position allows us to estimate the lateral placement of the NV inside the diamond nanostructure.
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All authors Nikhita Khera, Ephraim Spindler, Yanis Abdedou, Marcel Gasser, Sandra Wolff, Bert Lägel, Robert Frömter, Mathias Weiler, Mathias Kläui, Elke Neu
Optics
Universal Function Approximation via Diffractive Optical Processors: Physical Limits, Error Bounds, and Learnability
Md Sadman Sakib Rahman, Che-Yung Shen and Aydogan Ozcan
We present a unified theoretical framework connecting classical universal approximation theory,
Fourier-feature approximation, and diffractive optical processors. We show that phase-encoded diffractive processors implement finite
Fourier-feature expansions whose mathematical completeness follows from
Fourier/Stone-Weierstrass arguments, while their physical realizability is governed by finite coefficient synthesis through optimized spatially varying coherent point-spread functions (PSFs). Our analyses derive approximation-error bounds that separate
Fourier truncation, PSF-synthesis, input phase error, optical hardware, readout, and noise contributions; establish scaling relationships linking approximation complexity to optical degrees of freedom and input/output space-bandwidth products; derive
photon-budget and throughput limits imposed by
photon statistics; formulate finite-class statistical learnability bounds for phase-quantized diffractive function approximators; and analyze the impact of spatially incoherent illumination. We further analyze coherent optical cascadability and show that quadratic feature expansion through coherent mixing and optical readout provides a mechanism for enhanced representation while remaining fundamentally distinct from the depth-separation results established for digital neural networks. Our analyses provide a rigorous theoretical foundation for diffractive nonlinear function approximation and establish quantitative relationships among mathematical expressivity, optical hardware resources, statistical learning, and physical performance limits, thereby offering general design principles for large-scale analog optical computing systems.
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Optics
Design of a thermal loading resilient optical enhancement cavity for operation at 515 nm for X-ray production through inverse Compton scattering in an energy recovery linac
Alice Renaux, Aurelien Martens, Yann Peinaud et al. (+5 more)
A fast and simple method to optimize a high-power optical enhancement cavity is proposed. It is applied to a four-mirror bow-tie cavity operating at 515 nm, which is to be implemented within the PERLE ERL for the production of X-rays through inverse Compton scattering. The optimized figure of merit is the expected X-ray
photon rate. Thermal loading is carefully evaluated, giving also a path towards very high average power operation in infrared. One shows that
photon rates exceeding 10^11 per second at average energies above 280 keV in apertures of a few miliradians are within reach. For easier comparison with existing Compact X-ray sources providing high rates of
photons, the performance of the proposed design is also evaluated for a system delivering infrared
laser pulses. It is shown that a source delivering more than 10^13
photons per second is achievable with this design, an unprecedented performance for existing Compton X-ray sources. The design procedure employed here can be easily applied to other applications of high-power high-finesse optical cavities.
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All authors Alice Renaux, Aurelien Martens, Yann Peinaud, Ronic Chiche, Kevin Dupraz, Marie Jacquet, Daniele Nutarelli, Fabian Zomer
Optics
Photogalvanic second harmonic generation in Si3N4 for 1 Hz level on-chip metrology and spectroscopy
Andrei Diakonov, Roy Zektzer, Xiyuan Lu et al. (+2 more)
The coherent photogalvanic (PG) effect induces an effective $\chi^{(2)}$ nonlinearity in natively $\chi^{(3)}$ silicon nitride integrated photonics, unlocking pathways toward chip-scale precision spectroscopy and optical clockworks via second harmonic generation (SHG). While quasi-phase-matched PG-SHG using spatially varying internal electric fields offers tuning flexibility, it is often accompanied by pump-power- and detuning-dependent frequency offsets. Here, we investigate whether direct phase-matching—utilizing an intermodal scheme that generates a spatially uniform electric field—can support metrologically compatible SHG. By comparing the fundamental and doubled optical frequencies in a silicon nitride microresonator, we test the preservation of the (2:1) frequency ratio in directly phase-matched PG-SHG. We observe a frequency offset of $< 1\mathrm{~Hz}$, contrasting with previous limitations in quasi-phase-matched configurations. Furthermore, we measure a residual fractional frequency instability of $2\times 10^{-15}$ at $1\mathrm{~s}$, averaging down to the $10^{-16}$ level at $1000\mathrm{~s}$, with multi-hour deviations remaining below $1\mathrm{~Hz}$. These results establish directly phase-matched PG-SHG as a robust, metrologically compatible route to effective $\chi^{(2)}$ functionality, combining sub-Hz frequency-ratio fidelity and high coherence on a mature integrated platform for optical clockworks, self-referencing, and precision spectroscopy.
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All authors Andrei Diakonov, Roy Zektzer, Xiyuan Lu, Kartik Srinivasan, Liron Stern
Plasma Physics
On the relationship between the gain of Stimulated Raman Backscatter of a short-pulse laser in a plasma and the Pierce parameter for XFELs
Xinlu Xu and Warren Mori
It is shown that the convective gain of Stimulated Raman Backscatter (SRBS) within a single
laser wavelength in the strongly coupled regime is equivalent to the Pierce parameter commonly used to describe high gain x-ray Free Electron
Lasers (XFELs). The comparison utilizes the fact that the gain is a Lorentz invariant so the Pierce parameter is written in terms of the FEL parameters in the electron beam's rest frame. It is thus inferred that there is a direct correspondence of the physics between SRBS in the strong-coupled regime and high gain XFELs in the Compton regime.
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Instrumentation and Detectors · Cross-listed from cond-mat.supr-con
Microscopic theory of the field-induced instability of the vortex-free state in superconducting thin-film strips
Takayuki Kubo
In the Pearl–London theory, the edge-barrier-disappearance field of a superconducting thin-film strip depends on an arbitrary short-distance core cutoff because the
vortex is treated as a point object. The theory does not determine the cutoff or how it depends on temperature $T$, and therefore cannot determine the $T$ dependence of the instability field. Here we formulate the microscopic stability problem directly for the
vortex-free superconducting state. This removes the core-cutoff ambiguity and determines the instability field $B_s$ over the full temperature range and across all width regimes considered here. For a homogeneous dirty strip with negligible self-field, three width regimes occur. For $W<W_1(T)$, superconductivity disappears continuously into the normal state through a one-dimensional (1D) instability. For $W_1(T)<W<W_2(T)$, an edge-selective two-dimensional (2D) long-wavelength mode becomes unstable. For $W>W_2(T)$, the critical wave number is finite and the unstable mode is localized near an edge. In the wide-strip limit, $B_s\propto1/W$, recovering the Pearl–London scaling. In sufficiently narrow strips, however, the Pearl–London edge-barrier picture fails qualitatively.
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Computational Physics · Cross-listed from cond-mat.stat-mech
The two-particle-irreducible vertex of the two-dimensional lattice $\phi^4$ model across the Ising transition
Lode Pollet
We reconstruct the 2PI vertex $\Gamma(k,p;q)$ from Monte Carlo measurements of the connected two-particle correlator for the two-dimensional single-component $\phi^4$
lattice field theory and follow it across the Ising transition. Resolving the vertex in the irreducible representations of the point group $C_{4v}$, we find that the instability is driven by the $A_1$ (
ferromagnetic) channel at zero transfer, whose leading
eigenvalue of the symmetrized Bethe–Salpeter kernel approaches unity. Substantial $B_1$ (nematic) and $B_2$ (diagonal nematic) contributions cooperate with $A_1$ across all system sizes, highlighting that the soft sector is multidimensional. In real space, the vertex is short-ranged away from criticality while it develops a power-law tail at the critical point. In the ordered phase, the $q=0$
eigenvalue collapses because the
ferromagnetic weight has condensed into the (one-particle-reducible) order parameter (or collective coordinate for a finite system), although finite-momentum fluctuations persist. By stripping the crossed-channel ladders, we obtain the fully irreducible vertex, which is a local contact – to a very good approximation. Inserted into the parquet and Schwinger–Dyson equations, this contact reproduces the Monte Carlo self-energy with an accuracy better than one-tenth of a percent. This provides a first-principles
benchmark of the dynamical local-vertex approximation (D$\Gamma$A). Additionally, we demonstrate that in the critical region, the physical solution of the parquet equations behaves as a repulsive fixed point, driven initially by a single order-parameter mode.
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Optics
All-Optical Field-Resolved Spectroscopy With Interferometric Nonlinear Cross-Correlations
Felix Ritzkowsky, Gian Luca Dolso, Benjamin Mazur et al. (+2 more)
Direct time-domain measurements of electric fields enable sub-cycle spectroscopy of light-matter interactions, but established techniques such as electro-optic sampling are constrained in their bandwidth by gate-pulse duration and phase-matching limitations. Alternative approaches have emerged in recent years based on asymmetric interferometric nonlinear cross-correlations with highly nonlinear media, and have demonstrated, for example, the field-resolved study of
exciton ensembles. However, these nonlinear cross-correlation-based techniques have been benchmarked almost exclusively by self-referenced pulse characterization rather than by their quantitative spectroscopic performance, and all-optical approaches have received less
attention than those based on direct charge emission. Here we extend all-optical asymmetric interferometric cross-correlation to higher nonlinearities in sub-wavelength films and demonstrate field-resolved spectroscopy of the free-induction decay of two ro-vibrational bands of ambient water vapor with a performance comparable to state of the art electro-optic sampling. The measurement spans 190 THz of bandwidth (80 THz to 270 THz) with sub-500 GHz spectral resolution, a spectral intensity dynamic range of six orders of magnitude, and a field-strength noise floor of 100 kV per meter. We anticipate the rapid adoption of here presented all-optical sampling to many experimental settings and a broad impact beyond the ultrafast optics research community as it is drastically simplified in comparison to ionization based techniques and allows the translation of electro-optic-sampling-level sensitivity into higher frequency ranges not previously accessible by conventional tools.
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All authors Felix Ritzkowsky, Gian Luca Dolso, Benjamin Mazur, Matthew Yeung, Phillip D. Keathley
Applied Physics · Cross-listed from quant-ph
Engineering Nanodiamonds for Quantum Sensing: Material Constraints at the Nanoscale
Ashutosh Rathi, Keisuke Oshimi, Kento Sasaki et al. (+6 more)
Optically addressable solid-state
spin defects have emerged as powerful
multimodal quantum sensors, with nitrogen-vacancy (NV) centers in bulk diamond providing
benchmark quantum control and sensitivity under ambient conditions.
Embedding such defects in nanodiamonds (NDs) extends these capabilities to mobile probes capable of accessing complex biological and nanoscale environments. Reduced dimensions, however, introduce constraints beyond volumetric
spin impurities, notably enhanced
lattice strain and surface-induced noise sources, which shorten NV
spin relaxation times (T1 and T2) and destabilize the NV charge state, as well as resulting in pronounced particle-to-particle variability in NDs typically produced by top-down approaches. These effects complicate both sensing performance and the quantitative interpretation of
multimodal signals in realistic environments. This article provides a structured perspective on the physical mechanisms by which material properties constrain NV behavior in NDs, together with mitigation strategies that shape the robust use of these mobile
quantum sensors for biosensing and nanoscale science.
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All authors Ashutosh Rathi, Keisuke Oshimi, Kento Sasaki, Kensuke Kobayashi, Yutaka Shikano, Oliver Benson, Tim Schröder, Shery L. Y. Chang, Masazumi Fujiwara
Chemical Physics · Cross-listed from quant-ph
Impact of molecular orbital localization on quantum computational resources for Hamiltonian simulation: A benchmark study of hydrogen chain systems
Kenji Sugisaki, Yuhei Tachi, Masayoshi Terabe et al. (+1 more)
We investigate how molecular orbitals used as the basis of wave function expansion and how operator coefficient-based and locality-based
Hamiltonian truncation affects the computational cost of Trotter decomposition-based
Hamiltonian simulation in one-dimensional hydrogen chain systems. The analysis is performed using both Hartree–Fock canonical molecular orbitals (CMOs) and Pipek–Mezey-based localized molecular orbitals (LMOs). For short hydrogen chains, we evaluate the ground-state energy and fidelity and find that, in the CMO-based wave function expansion, introducing a threshold on
Hamiltonian coefficients is effective in reducing the gate cost while maintaining computational accuracy. In contrast, in the LMO-based wave function expansion, operator locality-based
Hamiltonian truncation is found to be more effective. By fitting the relationship between the truncation threshold and the ground-state energies and fidelities with empirical formulas, we estimate the threshold values required to achieve high fidelity ($F \ge 0.99$) in the ground-state wave function. Using the estimated thresholds, we then perform
quantum gate resource estimation for longer hydrogen chains up to H$_{100}$. The results suggest an exponential advantage of the LMO-based wave function expansion with
Hamiltonian truncation: the number of
quantum gates required for
Hamiltonian simulation grows polynomially when the CMO-based wave function expansion with operator coefficient-based
Hamiltonian truncation is adopted, whereas it grows polylogarithmically when the LMO-based wave function expansion is combined with operator locality-based
Hamiltonian truncation. These results provide useful guidelines for choosing orbital representations and
Hamiltonian truncation strategies in large-scale
quantum chemical simulations.
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All authors Kenji Sugisaki, Yuhei Tachi, Masayoshi Terabe, Hiroyuki Tezuka
Fluid Dynamics
Higher-Order Extensions of Weakly Viscous Dysthe Theory and a Phase-Lag Model for Nonlinear Mean-Flow Damping
C.M. Schober and A. Islas
We extend the Carter-Govan multiple-scales analysis of weakly viscous, narrowband deep-water wave packets beyond Dysthe order within the potential-flow reduction of Dias, Dyachenko, and Zakharov (DDZ). We seek to determine whether this framework generates the complex multiplier $(1 + i\beta)$ used phenomenologically to modify the nonlocal Dysthe mean-flow interaction. Although order counting places a direct viscous carrier-mean interaction at sixth order, it does not exclude an indirect fifth-order contribution arising from viscosity dependent lower-order harmonics and nonlinear interactions. We therefore derive the first correction to the induced mean flow and the complete fifth-order first-harmonic solvability condition. The resulting nonlocal terms are derivative–dependent and contain no explicit viscosity, excluding the proposed indirect mechanism within the DDZ framework. At sixth order, a restricted calculation of the nonlinear viscous block isolates a direct carrier-mean contribution with the same operator structure as the imaginary component of the prescribed mean-flow correction. Independently, a finite-adjustment-time model yields an exact, frequency dependent mean-flow response. Its low-frequency expansion produces the multiplier $ 1 + i\beta_{\mathrm{eff}}(\Omega)$, with $\beta_{\mathrm{eff}}(\Omega) =\Omega\tau.$ When $\Omega\tau = \mathcal O(\epsilon)$, the resulting phase-lag correction enters at fifth order, one order beyond the leading Dysthe mean-flow interaction.
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Fluid Dynamics
Interfacial dynamics and energy cascade in immiscible Rayleigh-Taylor turbulence
Dongxiao Zhao, Xiaoxue Huang and Gaojin Li
We investigate interfacial dynamics and multiscale energy transfer in immiscible Rayleigh-Taylor
turbulence using numerical simulations with varying surface tension coefficients $\sigma$. Capillarity is shown to control characteristic length scales, interfacial area, and global energy and enstrophy budgets. The flow exhibits self-similar
evolution with respect to surface tension, with the maximum kinetic energy scaling as $\sigma^{1/2}$ and the flow duration as $\sigma^{-1/4}$. A scale-by-scale budget shows that surface tension removes kinetic energy at large scales while injecting it at small scales, with the crossover occurring near the Hinze scale. We further recast and verify a local kinematic relationship between surface-tension power and interface stretching, up to conservative transport, $ \boldsymbol{f}^\sigma\cdot\boldsymbol{u} = - \sigma\mathcal{S}~|\nabla c| + \mathrm{Transport}$, where $\boldsymbol{f}^{\sigma}$ is the surface-tension force, $\boldsymbol{u}$ the velocity, $c$ the heavy-fluid volume fraction, and $\mathcal{S}$ the interface stretch rate. This relation links kinetic-energy transfer to the scalar-variance cascade and shows that energy transfer to the interface is governed by local strain. Statistics of individual bubbles and droplets reveal vertically elongated filaments with diameters of about three capillary scales, yielding a linear volume-area relation. Their vertical velocities scale with the square root of equivalent diameter, consistent with drag-buoyancy balance. These findings, particularly the direct link between surface tension power and resolved interface stretching, provide a rigorous physical framework for developing subgrid-scale closures for large eddy simulation of immiscible turbulent flows.
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Fluid Dynamics
Reliable and efficient steady CFD from surrogate predictions through Newton-Krylov correction
Mingcheng Lei, Weishao Tang, Yufei Zhang et al. (+1 more)
Neural surrogates offer a promising route to accelerating computationally expensive simulations governed by partial differential equations across science and industry. Their practical deployment, however, is limited by unreliable predictions under out-of-distribution (OOD) conditions. We develop a solver-coupled surrogate-Newton framework that uses surrogate predictions as high-quality initial guesses for Newton-Krylov iterations, thereby combining rapid global flow-field prediction with high-accuracy numerical convergence at the terminal stage. On an OOD
benchmark comprising geometries sampled from actual transonic airfoil optimization trajectories, the framework lowers the median residual L_2 ratio by over seven orders of magnitude while substantially reducing field and aerodynamic errors. In practical supercritical airfoil optimization, it improves online prediction reliability while achieving a 15.5-fold generation-level speedup over CFD. We further test the framework's extension to three dimensions using a flying-wing
dataset. Together, these studies demonstrate the potential of surrogate-Newton coupling to deliver accurate, efficient and scalable steady CFD across industrial workflows.
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All authors Mingcheng Lei, Weishao Tang, Yufei Zhang, Haixin Chen
Plasma Physics
Polarization-resolved attosecond gamma-ray emission from few-cycle laser interactions with cone targets
De-Sheng Zhang, Cui-Wen Zhang, Xue-Ren Hong et al. (+3 more)
Linearly polarized attosecond $\gamma$-ray pulses in the MeV range are generated from a cone target irradiated by a single few-cycle
laser pulse. Electron layers are periodically extracted from the cone walls and subsequently accelerated. Their interaction with the counter-propagating reflected attosecond field produces high-energy
photons through nonlinear Compton scattering (NCS), forming attosecond $\gamma$-ray pulses. We model this interaction using two-dimensional
quantum electrodynamics particle-in-
cell (QED-PIC) simulations that resolve electron
spin and
photon polarization during emission. The results show a shortest equivalent duration of $300\,\mathrm{as}$, with a corresponding linear polarization degree of 0.78. The
photon spectrum extends to $6\,\mathrm{MeV}$, and the linear polarization degree in the high-energy range reaches 0.88. The linear polarization degree remains high when
photons from both emission directions are collected over wide momentum-angle ranges. Scans over the cone opening angle and the coupled
laser-
plasma parameters reveal tradeoffs among
photon number, mean
photon energy, and polarization. Such highly polarized attosecond $\gamma$-ray pulses could be used to investigate ultrafast
nuclear dynamics and polarization-dependent processes in strong-field
quantum electrodynamics.
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All authors De-Sheng Zhang, Cui-Wen Zhang, Xue-Ren Hong, Feng Wan, Jian-Xing Li, Bai-Song Xie
Fluid Dynamics
Expansion of a hole in a viscoelastic liquid sheet
Tachin Ruangkriengsin, Rodolfo Brandão and Howard A. Stone
Experiments on highly viscous polymeric films show that punctured holes expand exponentially in time, without sustained accumulation of
liquid near the rim. This response departs from the Taylor–Culick description, in which displaced
liquid accumulates in a growing rim that moves at constant speed. Although these differences were initially attributed to viscoelasticity, they were later rationalized using a purely viscous theory, leaving the role of viscoelastic stresses unresolved. We analyze the expansion of an axisymmetric hole in a freely suspended viscoelastic
liquid sheet described by the Oldroyd-B model. Exploiting the separation of length scales between hole radius and film thickness, we derive extensional thin-film equations on the scale of the hole and an effective boundary condition from an asymptotic force balance in the tip region. Analytical solutions are obtained for weak viscoelasticity, $Wi\ll 1$, and the ultra-dilute limit, $\mu_p\ll\mu_s$, where $Wi$ is the Weissenberg number, while $\mu_s$ and $\mu_p$ are solvent and polymeric viscosities, respectively. For weak viscoelasticity, the dimensionless hole radius grows approximately as $e^{(0.5+\alpha Wi \beta_p)T}$, where $\alpha=(12 - 6\log 2-\pi)/21\approx 0.224$ and $\beta_p=\mu_p/(\mu_s+\mu_p)$. In the ultra-dilute limit, the radius grows approximately as $e^{(0.5+\alpha^{*}\beta_p )T}$, where $\alpha^{*}(Wi)>0$ is evaluated numerically. In both regimes, viscoelastic stresses increase the exponential growth rate relative to the Newtonian limit and induce film-thickness variations, with thickening near the retracting edge. This acceleration arises from azimuthal stretching and radial compression of the
polymers, which redistribute stresses in the film and modify the stress balance at the tip, leading to a stronger outward radial extensional flow.
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Optics
Xi Liu and Wenxi Fang
We analyze the integration of
quantum optical phenomena, such as cavity
quantum electrodynamics (CQED), Fabry Perot resonances, and strong light-matter coupling, into the design and engineering of next generation photovoltaic systems. We examine how these phenomena can be harnessed through photonic structures including optical cavities, plasmonic materials, and metasurfaces to improve light trapping, absorption, and carrier dynamics in future
solar cell devices. Specific focus is given to
semiconductor materials such as perovskites, organics, transition metal dichalcogenides (TMD), cadmium telluride (CdTe), and silicon. For perovskite
solar cells, we analyze device architectures, interfacial engineering with hyperbranched
polymers, and additive optimization using molecular dopants and nanosheets to enhance film morphology and stability. We further examine
laser-based metrology for thin-film characterization and coherent spectroscopy techniques involving frequency combs and high-harmonic generation. The paper also shows how machine learning (ML), combined with density functional theory (DFT), accelerates material screening and performance prediction for next-generation
solar cell absorbers. These developments demonstrate how
quantum optoelectronic design principles are transforming photovoltaic research and enabling higher efficiency, stability, and functionality in
solar energy devices.
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Fluid Dynamics
Beyond the Mean-flow: A Spectral-Dynamic Approach to Unraveling the Physics of Droplet Capture in Fog Harvesting Meshes
Pradyumna Das, Ranjan Ganguly and Ashoke De
Fog harvesting efficiency with mesh collectors is governed by complex interactions between droplet inertia and geometry-induced flow structures. Although previous studies have primarily relied on mean-flow metrics, the present work introduces a spectral-dynamic framework to examine an important but often overlooked control on droplet capture. A two-way coupled Eulerian-Lagrangian model is used to simulate droplet-laden flow (2-40 microm) across five representative mesh geometries. The results show that capture efficiency correlates not only with the magnitude of velocity fluctuations, but also with their spectral distribution and persistence. Frequency-domain analysis indicates that mesh geometry redistributes fluctuation energy across pore and obstruction regions, thereby defining a characteristic flow timescale. By comparing this flow timescale with the droplet response time, a dynamic matching parameter, {\Pi}= droplet response time/flow time scale, is introduced. The highest capture efficiency occurs when {\Pi} is order unity, corresponding to sustained droplet-flow interaction in the near-mesh region. Geometries that generate broadband, moderately amplified spectral content (e.g., triangular mesh) increase droplet residence time and interception probability, whereas geometries with either weak or highly localized fluctuations reduce performance through insufficient forcing or premature bypass. A physics-inspired correlation for capture efficiency is proposed based on this condition. The study therefore provides mechanistic design guidance, rather than a definitive optimum, for geometry optimization in fog-harvesting meshes.
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Physics and Society · Cross-listed from math.PR
The rank and layer distributions in random recursive trees
Huck Stepanyants, P. L. Krapivsky, Harrison Hartle et al. (+1 more)
The distribution of node depths in a network is crucial for analyzing network structure. Two measures, rank and layer, quantify how deep inside a network a node is. The rank is the node's distance to the closest leaf, a node of degree 1. The layer is the number of times all leaves must be stripped off for the node to become a leaf. We derive exact recursive expressions for the rank and layer distributions in random recursive trees. We show that the rank and layer distributions decay factorially and geometrically, respectively, and prove the self-averaging of the numbers of nodes with fixed rank or layer. Unlike previous studies, our approach does not depend on labels or a root node, providing a more versatile framework for analyzing rank and layer distributions in complex networks.
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All authors Huck Stepanyants, P. L. Krapivsky, Harrison Hartle, Dmitri Krioukov
Geophysics
Regional Chaos Synchronization towards controlling high-dimensional open environmental systems
Yohei Sawada
Although controlling chaos can be regarded as a form of chaos synchronization, conventional chaos synchronization does not provide a practical framework for controlling high-dimensional open chaotic systems, such as weather. In high-dimensional open environmental systems, it is simply impossible to make the difference between drive and response systems asymptotically approach zero over the entire domain. Instead of conventional global chaos synchronization, here I define regional chaos synchronization, in which state variables within only a small target region are synchronized with a target trajectory using actuators located in the target region. Theoretical considerations and numerical experiments show that the performance of regional chaos synchronization is substantially degraded by the injection of errors from exterior regions that the controller is not intended to modify. Even under the same actuator specifications, the performances of regional chaos synchronization differ among trajectories, which is not the case of conventional global chaos synchronization. An appropriate target trajectory differs substantially from the natural trajectory only in the target region. This choice of target trajectories can minimize the injection of errors from exterior regions and thereby enable successful regional chaos synchronization. The implications of this new framework for realistic control problems such as weather control are discussed.
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